Hybrid Waterborne Polyurethane/Graphitic Carbon Nitride\nNanosheet Films for Self-Cleaning and Anti-Bacterial Applications

The\nself-cleaning and antibacterial properties of waterborne polyurethane\n(WPU) films are realized by constructing a micronano structure on\nits surface via the controlled aggregation of graphitic carbon nitride\n(g-C<sub>3</sub>N<sub>4</sub>) nanosheets. Based on the hydrogen bonding\nbetween the CO groups in WPU and NH- groups in g-C<sub>3</sub>N<sub>4</sub>, the g-C<sub>3</sub>N<sub>4</sub> nanosheets can be\nwell dispersed in the WPU films. Further increasing the concentration\nof the g-C<sub>3</sub>N<sub>4</sub> nanosheets in the WPU dispersion\nduring the coating causes the enrichment of the g-C<sub>3</sub>N<sub>4</sub> nanosheets, triggering a minor aggregation and forming a\nconcave-like structure with nm to μm scale on the surface. Due\nto the photocatalytic capability of the g-C<sub>3</sub>N<sub>4</sub> nanosheets, free radicals are formed when exposed to visible light\nillumination, which, together with the large specific surface area\nof the micronano structure, decompose common stains on the WPU surface.\nMore than 95% of daily lives stains, such as soy sauce, can be removed\nfrom the hybrid WPU films with micronano structure on the surface\nafter exposure to visible light for only 1 h. Besides hydrophilic\nstains, the hybrid WPU films with micronano structure on the surface\nare also highly resistant against lipophilic stains and exhibit antibacterial\nproperties. 99.8% of S. aureus bacteria\nand 100% of E. coli bacteria can be\nefficiently killed on the hybrid WPU film surface after exposure to\nvisible light for 2 h. Based on these unique properties, the hybrid\nWPU films with micronano structure on the surface are highly suitable\nfor the interiors of cars, indoor furniture, or faux-leather garnets.